1. Field of the Invention
This invention relates to a process for the production of oval chain links from pieces of round wire having a given uniform length, in which, in a single bending station, a straight piece of wire, intersecting at right-angles the longitudinal axis of a cylindrical bending mandrel having an annular groove extending round this axis in a vertical plane to receive the piece of wire, is carried next to the mandrel at the level of the groove; the piece of wire is first bent on the mandrel into a V-shaped piece with the arms of the V at an obtuse angle; the middle of the piece of wire, forming the back of the link, is moved into a recess on the mandrel at its feed side and at the level of the aforesaid groove; and the piece of wire which has thus been subjected to its initial bending is bent into the groove outside the mandrel recess until the longitudinal axis of the piece of wire follows the course of the groove.
The invention further relates to an apparatus for carrying out such a process, comprising a single bending mandrel which has a recess on the side facing the wire feed to receive the outwardly concavely curved rear section of the unwelded chain link, the middle of which recess is situated opposite a holder provided to secure a piece of wire, which holder is movable backwards and forwards at right-angles to the longitudinal axis of the mandrel; further comprising two wire bending tools arranged symmetrically on either side of the mandrel and holder, which bending tools are displaceable in a transverse plane which contains the direction of displacement and is perpendicular to the axis of the mandrel, so as to move forwards towards the two ends of the wire positioned between the mandrel and the holder from the side of the mandrel facing the holder to the side remote from the holder; and comprising an arrangement for positioning the piece of wire between the mandrel and the holder, said arrangement having a wire feed sleeve which is either displaceable together with one of the two tools or stationary, and an abutment member situated axially opposite said wire feed sleeve for the abutment of the leading free end of the wire piece.
2. Description of the Prior Art
A known chain link bending machine of the generic type mentioned above, is suitable for carrying out a process of the type described above and is used for processing so-called pins. In this apparatus, the piece of wire in the feed sleeve is pushed completely out of the sleeve by the next following piece of wire between two rollers used as bending tools and the holder remote from the mandrel on one side and the mandrel on the other side until it touches the stationary support surface of the abutment member which is in the form of a peg. In this movement, there is no lateral distance between the piece of wire and the mandrel on one side and holder on the other and the wire therefore contacts these parts but makes no contact with the bending rollers which are situated remote from the mandrel and opposite the free ends of the wire piece at the same vertical distance apart. The wire piece placed in the operative position for bending is thus clamped by the mandrel and the holder and its two ends touch the flat end face of the abutment peg and, respectively, the leading free end of the next piece of wire which is now inside the feed sleeve. For the initial bending of the piece of wire to a V-shape by means of two back bending steels, the said bending steels grip the two ends of the piece of wire perpendicularly to its longitudinal axis and the two ends are swung about the middle of the wire piece, which is supported by the holder, while the back of the unwelded chain link is formed from the piece of wire. The holder then pushes forwards against the mandrel by an amount equal to the so-called camber of the bend at the back of the link, and the middle of the now V-shaped piece of wire is moved into the recess of the mandrel. Lastly, the back bending steels and at the same time the bending rollers are moved past the mandrel and at the same time the bending rollers grip the as yet straight ends of the V-shaped wire which is now clamped at its middle between the mandrel and the holder, and the bending rollers bend the ends of the wire through more than 90.degree. to place them round the mandrel until they form the preliminary C shape of the future chain link. In the known chain link bending machine, the piece of wire which has been bent into its preliminary C shape is closed to form the O-shaped link in one and the same station.
In the known chain link bending machine and its mode of operation, it would appear to be a disadvantage, in spite of the load being taken off the mandrel during the initial bending of the pins into their V shape, that additional time is taken up owing to the use of special back bending steels and the movement of the holder required for this purose. The output of unwelded chain links from this machine is therefore not as great as it could be if the above mentioned measures for reducing the load on the mandrel were not taken.